1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method and more particularly to an image processing apparatus and an image processing method for synthesizing a plurality of images photographed from multiple viewpoints to produce a refocused image.
2. Description of the Related Art
An image refocusing method has been known which produces, from pictures taken from a plurality of viewpoints, an image that is refocused at a desired virtual focal distance by subjecting them to an image position alignment operation and an image synthesizing operation (see Japanese Patent Laid-Open No. 2011-22796 and “Uncalibrated Synthetic Aperture for Defocus Control,” by Natsumi Kusumoto et al., CVPR, page 2552-2559, IEEE, (2009)). According to an invention, which is disclosed in Japanese Patent Laid-Open No. 2011-22796 and also presented in “Uncalibrated Synthetic Aperture for Defocus Control,” by Natsumi Kusumoto et al., a refocused image is produced by using a plurality of images shot at different photographing positions, shifting or deforming the individual images according to their photographing positions and a distance to an object one wishes to focus on and then synthesizing them.
The method discussed in “Uncalibrated Synthetic Aperture for Defocus Control,” by Natsumi Kusumoto et al., improves the image quality of out-of-focus areas outside the depth of field by generating intermediate viewpoint images between photographed images by estimation. This method, however, has a problem that the generation of intermediate viewpoint images produces an effect of blurring even an area one wishes to focus on. Another problem of this method is that as the resolution of an output image is increased, a large number of intermediate viewpoint images are required for creating a smooth blur gradation, entailing huge calculation costs. It is therefore an object of this invention to improve the quality of an area to be held in focus while reducing the calculation cost for generating the intermediate viewpoint images.